Laconic / Intelligible Unintelligible

The characters in the story know what they're saying; the audience does not.
"Draghghit blolblboloo fwisksza POOVOO!"
"...Why yes, that IS a link to the unabridged version. Thanks for that."

http://tvtropes.org/pmwiki/pmwiki.php/Laconic/IntelligibleUnintelligible